Metallurgical coke is a solid carbon fuel and carbon source used to melt and reduce iron ore in the production of steel. During an iron-making process, iron ore, coke, heated air and limestone or other fluxes are fed into a blast furnace. The heated air causes combustion of the coke which provides heat and a source of carbon for reducing iron oxides to iron. Limestone or other fluxes may be added to react with and remove the acidic impurities, called slag, from the molten iron. The limestone-impurities float to the top of the molten iron and are skimmed off.
In one process, known as the “Thompson Coking Process,” coke used for refining metal ores is produced by batch feeding pulverized coal to an oven which is sealed and heated to very high temperatures for 24 to 48 hours under closely controlled atmospheric conditions. Coking ovens have been used for many years to covert coal into metallurgical coke. During the coking process, finely crushed coal is heated under controlled temperature conditions to devolatilize the coal and form a fused incandescent mass or slab of coke having a predetermined porosity and strength. Because the production of coke is a batch process, multiple coke ovens are operated simultaneously, hereinafter referred to as a “coke oven battery”. For the purposes of this disclosure, the term “incandescent coke” means the normal state of coke when it is discharged from a coke oven. Incandescent coke is typically discharged from a coke oven at a temperature ranging from about 980° to about 1320° C.
In a conventional coke oven process, once the coal is “coked out”, the coke slab is pushed from the coke oven so that it breaks up and drops into a hot car wherein the coke is quenched with water to cool the coke below its ignition temperature. The quenching operation must be carefully controlled so that the coke does not absorb too much moisture. Once it is quenched, the coke is screened and loaded into rail cars or trucks for shipment.
One of the problems associated with the coke making process is dusting problems associated with removing the hot coke from the oven and dropping the coke into a quenching car as the coke is discharged from the coke ovens. As the coke drops into the quenching car, a significant amount of coke dust is created. Likewise, the quenching step produces steam and particulate matter as the coke is quenched. In fact, the largest single source of particulate matter emissions in a coke making process occurs during the coke discharge and quenching operations. Accordingly, elaborate dust collection systems have been devised to capture dust particles generated as the coke is pushed into the quench cars. However, many of these systems rely on pressure drop through a device, such as baffles or multi-cyclones to obtain efficient particulate removal. However, conventional quench systems have very little available pressure drop available for high efficiency removal of particulate matter. In order to reduce the dusting problems associated with coal coking without significantly increasing coke oven cycle times, improved apparatus and methods for quenching coke are needed.
In accordance with the foregoing need, the disclosure provides a method and apparatus for quenching metallurgical coke made in a coking oven. The method includes pushing a unitary slab of incandescent coke onto a substantially planar receiving surface of an enclosed quenching car so that substantially all of the coke from the coking oven is pushed as a unitary slab onto the receiving surface of the quenching car. The slab of incandescent coke is quenched in an enclosed environment within the quenching car with a plurality of water quench nozzles while submerging at least a portion of the slab of incandescent coke by raising a water level in the quenching car. Subsequent to quenching the coke, the planar receiving surface is tilted to an angle sufficient to slide the quenched coke off of the planar receiving surface and onto a product collection conveyer and sufficient to drain water from the quenched coke.
Another embodiment of the disclosure provides a movable apparatus for reducing dusting during a coke quenching step of a metallurgical coke making process. The apparatus includes a substantially fully enclosable quenching car adapted to receive a unitary slab of incandescent coke. The quenching car has an enclosable structure having a tiltable water quenching table disposed between a coke inlet end having an inlet door and a coke discharge end opposite the inlet end, the discharge end having a coke discharge door. Water spray nozzles are disposed between the inlet end and the discharge end above the quenching table. A water quenching sump is provided below the water quenching table for submerging a portion of the slab of incandescent coke in quench water. A dust collection system is attached to the enclosable structure for collecting water droplets and particulates from the coke quenching step.
The method and apparatus described above provide unique advantages for coking operations. In particular, flat pushing of the coke onto a quench car as a unitary slab of incandescent coke may significantly reduce an amount of particulate matter generated during a coke oven discharge operation. Accordingly, dust collection equipment for collecting particulate matter during the coke discharge operation may be substantially smaller and may provide higher dust collection efficiencies. Another advantage of the method and apparatus disclosed herein may be the simplicity of operation and the elimination of structures and equipment necessary to quench the coke and handle the quenched coke product. For example, the dust collection system has no moving parts and may rely only on pressure generated in a substantially enclosed chamber as a motive force for gas flow through the dust collection system.